Pilot Study on Flow Structure Around Floating Dikes

Spur dikes are applied extensively in waterway regulation practice. However, they may fail due to difficulty in increasing flow aspect ratio while not increasing sediment transport for target river branch simultaneously. Moreover, it is a challenge to control the regulation process and post-maintenance of the permanent spur dike structure. One alternative is to use a floating dike. Although floating dikes have been applied to guide floating debris in the hydropower industry, for e.g. by destroying the harmful vortex at the intake of a hydropower plant, existing studies on the flow dynamics around these structures are confined to surficial velocity fields. There is a clear gap in the literature to understand the flow structure around floating dikes. In the present paper, the flow around floating dikes is investigated systematically using 3D numerical modeling. The effect of dike geometry and structural layout on the flow dynamics is considered. The study revealed that the flow is altered largely by the floating dike structure. In the upper domain of the river, the velocity adjacent to the floating dike decreased, while the velocity below the floating dike increased. The turbulent intensity increased largely around the floating dike. The impact of geometry dimensions on the flow structure demonstrated that the maximum velocity and turbulent intensity increase as the immersed depth of a floating dike increased. Similarly, the maximum velocity and turbulent intensity increase with increasing width of the floating dike. A threshold length Lc of the structure was observed; when the length is larger than Lc, the maximum velocity and turbulent intensity decrease with increasing length; when the length is smaller than Lc, the maximum velocity and turbulent intensity increase with increasing dike length.